Interpretive Summary: The redbay ambrosia beetle (RAB) is an exotic wood-boring insect that vectors a fungal pathogen responsible for laurel wilt disease. Laurel wilt has caused high mortality in native redbay and swampbay trees in South Carolina, Georgia, and north Florida, and now poses an imminent threat to avocado production in south Florida. While chemical control of RAB is not viewed as the primary solution, immediate control tactics are needed by Florida avocado growers. A scientist at SHRS worked collaboratively with the University of Florida to conduct field and laboratory tests to evaluate efficacy of contact and systemic pesticides for RAB. Among the contact insecticides tested, zeta-cypermethrin+bifentrin and lambda-cyhalothrin+thiamethoxam provided the most consistent control. Fenpropathrin, crylite Na Al fluoride, and lambda-cyhalothrin+thiametoxam reduced beetle entry on treated avocado trees. Acetamyprid+Li 100 and the mixture of imidacloprid+cyfluthrin reduced RAB entry on treated swampbay trees. This information will be used by avocado growers and homeowners for improved management of the beetle vector, which will help control the spread of this lethal plant disease.

Technical Abstract: The redbay ambrosia beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), is an exotic pest of Lauraceae in the southeastern U.S. This wood-boring insect vectors a lethal fungus, Raffaelea lauricola, the causal agent of laurel wilt disease. The vector-pathogen complex is responsible for extensive mortality of native Persea trees in South Carolina, Georgia, and northern Florida, and now poses an imminent threat to the avocado (Persea americana) industry in south Florida. While chemical control of the vector is not viewed as the primary solution, control tactics should be made available to Florida avocado growers. Field and laboratory tests were conducted using avocado logs, potted avocado trees, and field grown swampbay trees (P. palustris) treated with contact and systemic pesticides. In general, zeta-cypermethrin+bifentrin and lambda-cyhalothrin+thiamethoxam provided the most consistent control of Scolytinae as contact insecticides, while methomyl, malathion, bifenthrin and endosulfan were more variable in results. Fenpropathrin, cryolite Na Al fluoride and lambda-cyhalothrin+thiametoxam showed less beetle entry on treated avocado trees than on the untreated control trees. Acetamyprid+Li 100 and the mixture of imidacloprid+cyfluthrin resulted in fewer entrance holes in swampbay trees; however, no statistical differences were observed in disease severity on treated versus non-treated avocados or swampbay. Linear regression models between the number of RAB holes per tree (x) and LW disease severity (ya) and between RAB entry holes per tree (x)and recovery of R. lauricola (yb) were both significant.